The German Society for Chemistry and Physics Education (GDCP)’s annual conference started out with a 2 hour cruise on Kiel fjord, during which the participants had the opportunity to choose between enjoying the sunshine and just doing whatever they liked, and several “guided tours” on either the sights of Kiel in general, or the biggest sight in Kiel, the water :-)
Preparation is everything: charts to learn to observe waves
I had prepared laminated charts to be used in case for some reason the weather wasn’t cooperating, and they definitely came in handy even during beautiful sunshine. On those charts, I used pictures that you’ve seen on this blog before, and contrasted them with typical physics text book illustrations, either sketches or ripple tank photos.
Since I was fairly busy talking, I only snapped two pictures:
The Oslo ferry right after turning inside the Kiel fjord, right when it starts backing up towards its berth, and, more interestingly, the turbulent wake. See how messed up the wave field is? It’ll take quite a while for all that turbulence to dissipate and for the sea surface to look as if nothing ever happened there!
And then our ferry’s wake. Here we see the turbulent propeller wake and one side of the feathery wavelets of the V formed by the wake.
Beautiful day to be on a ship!
Now, if you’d like to do a guided wave watching tour, you know where to find me… ;-)
So many people are surprised when I speak of wave watching as of a “real activity”. But to me it is! So I am going to talk you through a couple of minutes I spent looking out on the water where the Kiel Canal meets the Kiel fjord, right outside the locks at Kiel Holtenau.
A light breeze across the fjord
The “light breeze” part is fairly easy to observe: There are ripples on the water, but no actual waves. “Across the fjord” is also fairly obvious if you look at either side of the wave breaker: On the fjord side, there are ripples, on the shore side, there are none (or hardly any), indicating that the wave breaker is sheltering the shore-side from the wind (and dampening out the waves that come across the fjord).
And then: A ship sails into view!
We watch the ship sail past, dreaming of foreign countries and exciting adventures.
A ship leaving a wake
Behind the ship, the water looks very different from what it looks like everywhere else. The wake is turbulent and waves radiate outwards like a V, with the ship always at its tip.
Then, the ship is gone. But we can still see where it went.
There are no waves in the tubulent wake
The ship’s path is completely smooth. No waves have invaded the turbulent waters of the wave just yet, claimed them back. However, the waves the ship created in that V are about to reach the wave breaker.
Also the wind has picked up a little, as evident from the less smooth water surface shore-ward of the wave breakers.
Diffraction at a slit
Right after the waves from the V reach the wave breaker, they reach the opening at the end between the pylons. And what happens now is that the waves get diffracted at a “slit”: they propagate outwards as semi circles, even though the wave fronts were straight when they reached the slit.
How awesome is that? And all of this happening in a matter of minutes!
The weather changes
I said earlier that there was hardly any wind. Later that afternoon, it still wasn’t very windy, but the wind direction had changed: now the smooth and sheltered part has moved to the other side of the wave breakers. There are a lot more waves on the shore side of the wave breaker now, the ones with crests parallel to the wave breaker due to it moving, and the ones with crests perpendicular to it generated by wind. And you see gusts of wind on the sea side of the wave breakers in the different surface roughness.
So if you were wondering, too: That’s the kind of stuff I look at when I am wave watching. And I still find it super fascinating and relaxing at the same time! :-)
Last week, we ran an “expedition learning” course for 17-year olds. They were separated into several groups, working on different topics, and mine (unsurprisingly) worked on waves. You can see here what kind of stuff we observed when first testing the stretch of coastline we wanted to do our expedition to. And now you’ll get a picture dump of the actual expedition.
We started out in not-so-ideal-but-really-not-too-bad-either kind of weather, as you can read off the tracks below: It had been raining a little, but not very hard, and it had stopped by the time we got there.
The drift lines looked quite promising.
My group dove right into it (only figuratively, luckily, not literally). However I wasn’t quite sure if this guy knew what he was getting into?
At this point we were still very close to the car, so I thought that it might be quite smart strategically to let them figure out here how high the waders go and what happens if the waves are higher than the waders… And the wakes of two ships meeting up at a headland are a very good place to learn about that kind of things!
This headland is a very good place to start observing waves in any case. Especially at the typical wind direction found here. Because then, looking back from the light house to the land, you see a large area that is sheltered where waves only build up gradually. Which is a very nice contrast to the waves arriving upwind and makes it very easy to observe differences.
And then if you look downwind from the headland, you see waves sneaking around the headland from both sides. Those coming from the right are from the fully developed wave field that has been growing all the way down Kiel fjord, and then those coming in from the left are the ones that only started growing downwind of the little barrier shown in the picture above.
Can you see it? Maybe easier on a panorama kind of picture?
Of course we always like to look at the ring waves that appear when other waves hit stones…
I didn’t foresee that wave watching would happen mostly from within the water, but the guys in my group made a good case for walking on the sand bank to actually measure the wave hight depending on the water depth (rather than just observing and estimating from dry land, as I would have done), but why not?
Luckily, they found the shallowest part of the sand bank in exactly the same spot I would have told them to look for it based on the wave field ;-)
Btw, a nice example of coastal dynamics right below. We had a coastal dynamics group, too, but I don’t even know if they looked at this kind of stuff, I mainly saw them taking soil samples.
And I know I made the same observation in the same spot last time, too, but I think it’s fascinating how the different directions of the ripples and drift lines and waves all come together.
In any case, a nice day at the beach!
Well, most of the time anyway.
Luckily, we found shelter!
Those, btw, are Annika and Jeannine, who were working with a different group on coastal vegetation.
But: New and interesting pattern on the beach once the rain was done!
The kids spent the next two days putting all their observations on maps and preparing a presentation, and I am really happy with how it turned out. Of course there is some room for improvement still, but how boring would it be if there wasn’t? ;-) All in all I think it was a pretty successful course!
When I said that wake watching made me happy last week, did you really think those were all the wakes I was going to show you? Ha! No, I have plenty more! :-)
Today, I want to show you a couple that have one thing in common: the way that they show up against the sun’s reflection and thus become a lot more visible than they would be if they were just reflecting a uniformly blue or grey sky.
Let me tell you the story of the picture below. I was walking along Kiel fjord with some friends and we saw this mama duck with all those tiny cute ducklings. We stopped and oooo’d and aaaaa’d and they were just so adorable!! But the after a while they swam on and we continued walking. But then there were people standing on the sea wall, obviously very worried about something. And then we saw it: a tiny duckling that had gotten separated from its family! It was struggling so hard to catch up with the rest, but they were swimming together while the little one was trying to climb over the rocks along the sea wall! The distance grew larger and larger. People started cursing mama duck for leaving the little one, or were pleading with her to come back for the poor baby. And then mama duck started heading out into the open fjord, where it was a lot more windy and wavy. How should the poor baby ever catch up? Eventually mama duck turned back. But she didn’t spot the baby! They all swam in the wrong direction away from the baby! It was dramatic. The crowd on the promenade was agitated. People were heading towards the ladders to climb down and rescue the baby! Then, finally, mama duck and all the siblings came back. Baby duck sprinted back to its family and finally everybody was reunited. Phew! The crowd wasn’t quiet ready to leave, not quite trusting mama duck that she wouldn’t abandon baby duck again. But then we decided that we had seen the happy ending, the scar hadn’t hurt for 20 years and all was well.
The reason I am telling you this story? Because I am still fascinated by wakes of ducks. And I saw really beautiful ones this morning:
The structure inside of the legs of the V is clearly visible.
And what’s even better: you can see the pattern on the sea floor, too!
The more I observe waves, the better I get at noticing details that were probably always there but that never stood out to me as clearly as they do now.
That’s why I am so happy about having started this blog — it helps me observe so many amazing things :-)
Oh, and if you are still waiting for the wake? Sorry, this was it. I was obviously talking about waves :-)